A muffler usually has a housing, in which one or more chambers may be formed to assume different muffling functions. An intermediate or inner panel, which is supported at its edge on the housing to absorb loads, is advantageously arranged between adjacent chambers in the housing. Furthermore, it is common practice to permanently connect pipes, which extend in the housing, with such an inner panel. Frequent is in this connection a constellation in which such a pipe is fastened to the housing, on the one hand, and to such an inner panel, on the other hand. To avoid thermal stresses, it is advantageous, furthermore, not to fasten the inner panel on the edge to the housing but to arrange the inner panel loosely, preferably in a non-positive (not fixed) manner thereon in order to make possible relative motions caused by thermal effects between the housing and the inner panel. A kind of sliding fit can be formed, in principle, between a collar of the inner panel, which collar extends circumferentially at the edge, and the housing. It is possible for this, in principle, in case of a conventional mode of construction to bend the collar by about 90° in relation to the inner panel. The collar is flatly in contact with its outer side facing the housing radially with an inner side of the housing at least at ambient temperature in the mounted state.
The relative terms “axial” and “radial” pertain to a normal axis, which is located at right angles on a plane in which the respective inner panel extends.
The temperature of the muffler rises during the operation of the exhaust system, and the housing, on the one hand, and the respective pipe and the respective inner panel, on the other hand, may undergo different thermal expansions. This is due, on the one hand, to the fact that the different components reach different temperatures. On the other hand, the pipes carrying exhaust gas within a muffler and the housing are usually manufactured from different materials, which possess different coefficients of thermal expansion. In particular, the inner panel may be manufactured from the same material as the pipe, so that the intermediate panel will also have an expansion different from that of the housing. However, the different temperatures may also lead to relative motions due to thermal effects even if the different components are manufactured from the same material or from similar materials. Therefore, embodiments in which the housing and the pipe are each manufactured from ferrite or each from austenite are also conceivable.
The heating of the muffler thus causes, on the one hand, an expansion or an adjustment of the pipe in its longitudinal direction relative to the housing. This leads to an axial displacement of the intermediate panel permanently connected to the pipe within the housing. Such an axial displacement can be compensated in a simple manner by the above-described axial sliding fit between the inner panel and the housing. On the other hand, the housing may undergo a greater expansion in the radial direction than the inner panel, for example, when the intermediate panel and the housing consist of different materials. As a consequence, the housing may be lifted off from said collar radially at least in some areas. This leads to the risk of loss of the non-positive connection (not fixed connection) between the housing and the inner panel, which is accompanied by a free mobility between the inner panel and the housing in the radial direction and in the axial direction. Based on vibrations, which occur during the operation of the exhaust system, undesired and disturbing noises may be generated. Further, there is a risk of increased abrasion and wear of the muffler. In addition, there is a risk of a significant damage to the components in case vibrations are induced in the arrangement comprising the pipe and the inner panel in the range of the natural frequency. Even total failure of the muffler may occur in an extreme case.